WO2022042496A1

WO2022042496A1 - Interface functional layer and preparation method therefor, and lithium ion battery

Info

Publication number: WO2022042496A1
Application number: PCT/CN2021/114119
Authority: WO
Inventors: 张赵帅; 赵伟; 李素丽; 李俊义; 徐延铭
Original assignee: 珠海冠宇电池股份有限公司
Priority date: 2020-08-31
Filing date: 2021-08-23
Publication date: 2022-03-03
Also published as: CN111834662A; US20230163421A1; CN111834662B

Abstract

The present application relates to an interface functional layer and a preparation method therefor, and a lithium ion battery. The interface functional layer comprises a cyclic ether compound, a lithium salt, an auxiliary, and ceramic powder at a mass ratio of 50-90:5-30:5-40:0-5. According to the present application, the interface functional layer is provided between a cathode and/or an anode and a solid electrolyte, such that uneven deposition of lithium ions in an interface gap is inhibited, the interface impedance is reduced, and the interface stability is improved.

Description

Interface functional layer and preparation method thereof, and lithium ion battery

This application claims the priority of the Chinese patent application with the application number 202010897495.8 and the application name "Interface functional layer and its preparation method and lithium ion battery" filed with the China Patent Office on August 31, 2020, the entire contents of which are incorporated by reference in this application.

technical field

The application belongs to the technical field of lithium ion batteries, and in particular relates to an interface functional layer and a preparation method thereof, and a lithium ion battery.

Background technique

In recent years, among various commercial chargeable/dischargeable chemical energy storage devices, lithium-ion batteries have the characteristics of high energy density and long service life, and have been attracting attention since they were put into the market. field is widely used. However, since the organic electrolyte is flammable and explosive, and also volatile, it is easy to cause safety problems in lithium-ion batteries. Therefore, researchers use solid electrolytes to replace electrolytes in order to fundamentally solve the safety problems of all-solid-state batteries. As the key material of all-solid-state lithium batteries, solid electrolytes can effectively improve the safety and stability of batteries due to their high mechanical strength, excellent density and ability to resist lithium dendrite growth.

Although traditional solid electrolytes have certain advantages in ionic conductivity, the interface between solid electrolytes and electrodes has always been an important challenge limiting the development of solid-state batteries. For example, there are generally space charge layers and defect structures at the solid-solid interface, and their physicochemical properties will affect the transport of ions and electrons, the stability of the electrode structure, and the rate of charge transfer. During the cycle of the battery, the CEI film on the positive electrode surface and the SEI film on the negative electrode surface have a certain influence on the cycle and capacity; the poor contact wettability of the solid-solid interface of the positive electrode and the electrolyte easily leads to an increase in the interfacial resistance of the electrolyte; The negative electrode metal lithium is active, and the interface problem with poor contact will lead to the uneven deposition of lithium dendrites at the interface.

Therefore, it is necessary to develop an interfacial functional layer that can stabilize the solid electrolyte and lithium anode.

SUMMARY OF THE INVENTION

The present application provides an interface functional layer. By arranging the interface functional layer between the positive electrode and/or the negative electrode and the solid electrolyte, the uneven deposition of lithium ions at the interface voids is suppressed, the interface impedance is reduced, and the interface stability is improved at the same time. sex.

The present application also provides a method for preparing the above-mentioned interface functional layer, which has the advantages of simple process, convenient operation, remarkable effect and convenient industrial production.

The present application also provides a lithium-ion battery with higher cycle efficiency and cycle stability, while the battery short circuit rate is almost zero.

The technical solution proposed in this application is:

In the first aspect, the present application proposes an interface functional layer, the interface functional layer includes a cyclic ether compound, a lithium salt, an auxiliary agent and a ceramic powder in a mass ratio of 50-90:5-30:5-40:0-5 .

The interface functional layer of the present application can improve the grain boundary resistance and electrode interface performance by adjusting the composition and ratio of raw materials, suppress the uneven deposition of lithium ions at the interface voids, reduce the interface impedance, and improve the interface stability at the same time.

The above-mentioned interface function layer of the present application may also have the following additional technical features:

In a specific embodiment of the present application, the interface functional layer is obtained by mixing the raw materials uniformly, and then attaching to the positive electrode, the negative electrode and/or the solid electrolyte, and performing curing treatment.

Specifically, the method of attachment is selected from one or a combination of blade coating, spray coating, casting and soaking.

The temperature of the curing treatment can be adjusted according to the raw materials of the interface functional layer. Generally, the temperature of the curing treatment can be adjusted to 25-60°C, such as 35°C, to obtain a uniform and stable interface functional layer.

Controlling the thickness of the interface functional layer within a certain range is beneficial to better control the ion passing rate and electrical conductivity. In the present application, the thickness of the interface functional layer is about 10 nm-10 μm, for example, 100 nm-1 μm, and further, the thickness of the interface functional layer is 400-800 nm.

The cyclic ether compounds, lithium salts, additives and ceramic powders in this application are all conventional materials in the art, which can be self-made or commercially available, which are not particularly limited in this application.

The use of nano-scale ceramic powder is more conducive to obtaining an interface functional layer with better electrical properties. Therefore, in the present application, the particle size of the ceramic powder is about 1-900 nm, for example, 400-800 nm, and further, the particle size of the ceramic powder is 500-600 nm.

In a specific embodiment of the present application, the cyclic ether compound is selected from 1,3-dioxane and/or 1,4-dioxane; and/or,

The lithium salt is selected from lithium perchlorate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium bis-oxalate borate, lithium oxalate difluoroborate, lithium bis-difluorosulfonimide, lithium bis-trifluoromethanesulfonate Lithium imide, lithium trifluoromethanesulfonate, bismalonate boric acid, lithium oxalate borate malonate, lithium hexafluoroantimonate, lithium difluorophosphate, 4,5-dicyano-2-trifluoromethane One or more combinations of lithium imidazolium, LiN(SO ₂ CF ₃ ) ₂ , LiN(SO ₂ C ₂ F ₅ ) ₂ , LiC(SO ₂ CF ₃ ) ₃ and LiN(SO ₂ F) ₂ ; and /or,

The auxiliary agent is selected from one or more combinations of ethylene glycol dimethyl ether, dipropylene glycol dimethyl ether carbon, ethylene acid, propylene carbonate, dimethyl carbonate and diethyl carbonate; and/or,

The ceramic powder is selected from one or several combinations of nano-hexagonal boron nitride, nano-alumina and nano-silicon dioxide.

In the second aspect, the present application proposes the above-mentioned preparation method of the interface functional layer, comprising the following steps:

After mixing the cyclic ether compound, lithium salt, auxiliary agent and ceramic powder with a mass ratio of 50-90:5-30:5-40:0-5, they are attached to the positive electrode, negative electrode and/or solid electrolyte and cured processing to obtain the interface function layer. Those skilled in the art can understand that during mixing, auxiliary stirring can be used to speed up the mixing, for example, adjusting the rotational speed to 200-1000 rpm/min and stirring for 1-24 hours, a uniformly mixed solution can be obtained. The cyclic ether compound, lithium salt and auxiliary agent can be mixed firstly until uniform, and then the ceramic powder is slowly added to facilitate the dispersion of the ceramic powder.

The application does not limit the types of negative electrodes. The negative electrode is selected from at least one of a metal lithium negative electrode or a lithium alloy negative electrode, the metal lithium is selected from one of molten metal lithium, lithium powder and lithium ribbon, and the lithium alloy includes Li-In alloy, Li- Al alloy, Li-Sn alloy, Li-Mg alloy and Li-Ge alloy.

In a specific embodiment of the present application, the method of attachment is selected from one or a combination of blade coating, spray coating, casting and soaking. Specifically, the temperature of the curing treatment is 25-60° C., for example, 35° C., and the interface functional layer after curing has a uniform and good morphology and less pore cracks.

The preparation method of the interface functional layer of the present application has the advantages of simple process, convenient operation, remarkable effect and convenient industrial production. By disposing an interface functional layer between the positive electrode and/or the negative electrode and the solid electrolyte, the uneven deposition of lithium ions at the interfacial voids is suppressed, the interfacial impedance is reduced, and the interfacial stability is improved at the same time.

In a third aspect, the present application proposes a lithium ion battery, which is prepared by winding or stacking a positive electrode, a solid electrolyte, and a negative electrode, and the above-mentioned interface functional layer is also provided between the negative electrode and/or the positive electrode and the solid electrolyte.

The lithium-ion battery can be manufactured by a conventional winding or lamination process. Specifically, the positive pole piece, the solid electrolyte, the interface functional layer, and the negative pole piece are wound or laminated together in sequence, and then vacuum-packed, The lithium ion battery can be obtained by welding the tabs.

The composition of the positive electrode sheet may include a positive electrode active material, a solid electrolyte, a conductive agent and a binder in a mass ratio of 70-95:1-15:1-10:1-10.

The composition of the positive electrode sheet includes a positive electrode material, a conductive agent and a binder. The active material in the positive electrode material can be selected from lithium iron phosphate chemical system materials, lithium cobalt oxide chemical system materials, nickel cobalt lithium manganate chemical system materials, lithium manganate chemical system materials, nickel cobalt lithium aluminate chemical system materials, nickel cobalt lithium aluminate chemical system materials Lithium manganese aluminate chemical system materials, nickel cobalt aluminum tungsten chemical system materials, lithium-rich manganese chemical system materials, lithium nickel cobalt oxide chemical system materials, lithium nickel titanium magnesium oxide chemical system materials, lithium nickelate chemical system materials, spinel One or a combination of lithium manganate chemical system materials and nickel cobalt tungsten chemical system materials.

The conductive agent may be selected from one or more of conductive carbon black (SP), ketjen black, acetylene black, carbon nanotube (CNT), graphene and flake graphite.

The binder may be selected from one or more of polytetrafluoroethylene, polyvinylidene fluoride and polyvinylidene fluoride-hexafluoropropylene.

The electrolyte may be a solid electrolyte or a liquid electrolyte.

The liquid electrolyte can be self-made or purchased from any commercial electrolyte in the market.

The electrolyte may be selected from a sulfide electrolyte, a perovskite type electrolyte, a Garnet type electrolyte, a NASICON type electrolyte, a LISICON type electrolyte, and a combination of one or more of the polymer electrolytes.

The sulfide electrolyte can be selected from lithium phosphorus chloride sulfur, lithium phosphorus bromide sulfur, lithium phosphorus iodine sulfur, lithium phosphorus silicon sulfur, lithium phosphorus aluminum sulfur, lithium phosphorus germanium sulfur, lithium phosphorus boron sulfur, lithium phosphorus sulfur, lithium silicon sulfur , one or a combination of lithium silicon indium sulfur and the like.

The perovskite electrolyte is Li _3x La _2/3-x TiO ₃ , wherein 0.04<x<0.17.

The garnet type electrolyte is lithium lanthanum zirconium oxygen electrolyte and its Al, Ga, Fe, Ge, Ca, Ba, Sr, Y, Nb, Ta, W, Sb element doped derivatives; further, the said The garnet-type electrolyte is Li _7-n La ₃ Zr _2-n _Tan O ₁₂ and/or Li _7-n La ₃ Zr _2-n _Nbn O ₁₂ , where 0≤n≤0.6; or Li _6.4-x La ₃ Zr _2-x Ta _x Al _0.2 O ₁₂ , wherein 0.2≤x≤0.5.

The NASICON type electrolyte is Li _1+x Al _x Ti _2-x (PO ₄ ) ₃ (LATP), where 0.2≤x≤0.5; and/or Li _1+x Al _x Ge _2-x (PO ₄ ) ₃ (LAGP), where 0.4≤x≤0.5.

The LISICON type electrolyte is Li _4-x Ge _1-x P _x S ₄ (X=0.4 or X=0.6).

The polymer electrolyte is selected from polymer electrolytes containing lithium salts. Wherein, the polymer is selected from polycarbonate, polyether, polyethylene glycol, polyphenylene ether, polyethylene diamine, polyethylene dithiol, polyester, polyethylene oxide, etc. and their copolymer derivatives.

The lithium ion battery of the present application can be a button battery, a mold battery or a soft pack battery.

In the lithium ion battery of the present application, an interface functional layer is arranged between the positive electrode and/or the negative electrode and the solid electrolyte, thereby suppressing the uneven deposition of lithium ions at the interface voids, reducing the interface impedance, and improving the interface stability at the same time. The lithium-ion battery of the present application has higher cycle efficiency and cycle stability, while the battery short-circuit rate is almost zero.

Additional aspects and advantages of the present application will be set forth, in part, from the following description, and in part will become apparent from the following description, or may be learned by practice of the present application.

Description of drawings

1 is a schematic structural diagram of the metal lithium negative electrode pole piece and the interface functional layer thereon according to Example 1 of the application;

2 is a schematic structural diagram of the solid electrolyte of Example 4 of the application and the interface functional layer thereon;

3 is a schematic structural diagram of the solid electrolyte of Example 7 of the application and the interface functional layer thereon;

4 is a microscopic topography diagram of the interface functional layer of Example 3 of the application;

FIG. 5 is a schematic diagram showing the comparison of the AC impedance of the lithium ion battery in Example 5 of the present application and Comparative Example 5;

FIG. 6 is a cycle diagram of the lithium symmetric battery of Example 8 of the present application at a current density of 1 mA/cm ² .

detailed description

The present application will be described in further detail below with reference to specific embodiments. It should be understood that the following examples are only illustrative to illustrate and explain the present application, and should not be construed as limiting the protection scope of the present application. All technologies implemented based on the above content of this application are covered within the scope of protection intended by this application.

The ceramic powders in the examples of the present application were purchased from: Kejing Chemical Co., Ltd., and the particle size was about 400-800 nm.

The present application is described in detail below by specific embodiments:

The test method of each embodiment and comparative example is as follows:

1. AC impedance at room temperature

Lithium-ion battery AC impedance test

Shanghai Chenhua CHI600E electrochemical workstation was used for testing, parameter setting: amplitude was 10mV, frequency range was 0.1Hz-3MHz.

2. Lithium symmetric battery cycle test

Using Wuhan blue battery test equipment;

Test conditions: The lithium symmetric battery constant current charge-discharge test was performed at a current density of 1 mA/cm ² .

3. Cycle life test

The test instrument is Wuhan Landian battery test equipment;

Test conditions: When the initial capacity is basically the same, the number of cycles when the capacity decays to 80% of the initial value is measured at 25°C and 0.2C/0.2C.

4. Battery short circuit rate test

During the cycle life test, the battery fails or is short-circuited, which means that it cannot be charged and discharged normally, which is recorded as a short-circuit. Cell short-circuit rate = number of short-circuited cells/total number of cells measured x 100%.

Example 1

Embodiment 1 proposes a lithium metal negative electrode and a lithium ion battery containing an interface functional layer, and the preparation method includes the following steps:

1. Preparation of metallic lithium anode with interfacial functional layer

(1) 1,4-dioxane, lithium bistrifluoromethanesulfonimide (LiTFSI), polycarbonate (PC), and nano-boron nitride (BN) are in a mass ratio of 79:9:10 :2 After mixing evenly, put it in a beaker, and evenly stir at 300rpm for 15h to form a homogeneous solution.

(2) After the stirring is completed, the homogeneous solution is uniformly coated on the surface of the metal lithium sheet by means of scraping, so that the homogeneous solution fully covers and infiltrates the metal lithium sheet.

(3) After 15 minutes of pretreatment, heating and curing, the curing temperature is 45° C., to obtain a metal lithium negative electrode containing an interface functional layer, as shown in FIG. 1 , wherein the thickness of the interface functional layer is 500 nm.

2. Preparation of lithium-ion batteries

Coated with lithium cobaltate (91wt%), Li _6.6 La ₃ Zr _1.6 Ta _0.4 O ₁₂ solid electrolyte (3.0 wt %), acetylene black (2.5 wt %), and polytetrafluoroethylene (3.5 wt %) A 6 mg/cm ² positive electrode piece, with Li _6.6 La ₃ Zr _1.6 Ta _0.4 O ₁₂ solid electrolyte, and the above-treated metal lithium negative electrode containing an interface functional layer, the existing lamination process is used to make a soft-pack lithium ion battery.

Comparative Example 1

Comparative example 1 proposes a lithium ion battery, and its preparation method includes the following steps:

Coated with lithium cobaltate (91wt%), Li _6.6 La ₃ Zr _1.6 Ta _0.4 O ₁₂ solid electrolyte (3.0wt%), acetylene black (2.5wt%), PVDF (3.5wt%) to an areal density of 6mg/cm The positive pole piece of ² is matched with Li _6.6 La ₃ Zr _1.6 Ta _0.4 O ₁₂ solid electrolyte, traditional untreated metal lithium negative electrode, and the existing lamination process is used to make a soft-pack solid-state lithium ion battery.

Example 2

Embodiment 2 proposes a metal lithium negative electrode and a lithium ion battery containing an interface functional layer, and the preparation method includes the following steps:

1. Preparation of Li-In alloy anode with interfacial functional layer

(1) Mix 1,3-dioxane, lithium hexafluoroarsenate (LiAsF ₆ ), DME, and nano-alumina in a mass ratio of 68:12:23:3 and place them in a beaker. The rotating speed of 600rpm was uniformly stirred for 8h to form a homogeneous solution.

(2) After the stirring is completed, the Li-In alloy is immersed in the homogeneous solution, so that the homogeneous solution fully covers and infiltrates the Li-In alloy.

(3) 9 minutes after the pretreatment, the Li-In alloy was taken out from the homogeneous solution, and heated and solidified at a solidification temperature of 35 °C to obtain a Li-In alloy negative electrode containing an interface functional layer, wherein the thickness of the interface functional layer was 400nm.

2. Preparation of lithium-ion batteries

Coated with LiNi _0.5 Co _0.3 Mn _0.2 O ₂ (74wt%), lithium phosphorus chloride sulfur solid electrolyte (11wt%), Super-P (9wt%), PVDF-HFP (6wt%) to an areal density of 12mg/cm ² The positive pole piece is matched with the lithium phosphorus chloride sulfur solid electrolyte, and the Li-In alloy negative electrode containing the interface functional layer after the above treatment, and the mold is used to make the lithium ion battery.

Comparative Example 2

Comparative example 2 proposes a lithium ion battery, and its preparation method includes the following steps:

Coated with LiNi _0.5 Co _0.3 Mn _0.2 O ₂ (74wt%), lithium phosphorus chloride sulfur solid electrolyte (11wt%), Super-P (9wt%), PVDF-HFP (6wt%) to an areal density of 12mg/cm ² The positive pole piece is matched with lithium phosphorus chloride sulfur solid electrolyte and traditional Li-In alloy negative electrode, and a lithium ion battery is made of a mold.

Example 3

Embodiment 3 proposes a lithium metal negative electrode and a lithium ion battery containing an interface functional layer, and the preparation method includes the following steps:

1. Preparation of Li-Cu composite anode with interfacial functional layer

(1) Mix 1,4-dioxane, lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), and EC/DEC (system ratio 1:1) uniformly in a mass ratio of 67:15:18 After placing it in a beaker, stirring at 800 rpm for 2 h to form a homogeneous solution.

(2) Immerse the Li-Cu composite tape in the homogeneous solution after the stirring is completed, so that the homogeneous solution fully covers and soaks the Li-Cu composite tape.

(3) 3 min after pretreatment, the Li-Cu composite tape was taken out from the homogeneous solution and cured at room temperature of 25 °C to obtain a Li-Cu composite negative electrode containing an interface functional layer, wherein the thickness of the interface functional layer was 800 nm.

2. Preparation of lithium-ion batteries

Coated with lithium iron phosphate (85wt%), polyethylene oxide polymer electrolyte (8%), CNT (5wt%), polyvinylidene fluoride (2wt%) to form a positive electrode sheet with an areal density of 10mg/ ^cm2 , matched with The polyethylene oxide polymer electrolyte and the Li-Cu composite negative electrode containing the interface functional layer after the above-mentioned treatment are made into a soft-pack solid-state lithium ion battery by using an existing winding process.

Comparative Example 3

Comparative example 3 proposes a lithium ion battery, and its preparation method includes the following steps:

Coated with lithium iron phosphate (85wt%), polyethylene oxide polymer electrolyte (8%), CNT (5wt%), polyvinylidene fluoride (2wt%) to form a positive electrode sheet with an areal density of 10mg/ ^cm2 , matched with Polyethylene oxide polymer electrolyte and Li-Cu composite negative electrode are used to make soft-pack solid-state lithium ion battery by the existing winding process.

Example 4

Embodiment 4 proposes a solid electrolyte and a lithium ion battery containing an interface functional layer, and the preparation method includes the following steps:

1. Preparation of solid electrolytes with interfacial functional layers

(1) Mix 1,3-dioxane, lithium hexafluorophosphate (LiPF ₆ ), PC/DMM (volume ratio 1:1), and nano-BN according to the mass ratio of 56:18:23:3 and place them on the In the beaker, stir uniformly at 500 rpm for 1 h to form a homogeneous solution.

(2) After the stirring is completed, the homogeneous solution is uniformly coated on the surface of the Li _0.3 La _0.56 TiO ₃ electrolyte near the positive electrode side by casting, so that the homogeneous solution fully covers the Li _0.3 La _0.56 TiO ₃ infiltrated near the positive electrode side. electrolyte.

(3) After pretreatment for 24 min, solidify at room temperature of 55° C. to obtain a solid electrolyte containing an interface functional layer, as shown in FIG. 2 , wherein the thickness of the interface functional layer is 300 nm.

2. Preparation of lithium-ion batteries

Coated with LiNi _0.8 Co _0.15 Al _0.05 O ₂ (80wt%), Li _0.3 La _0.56 TiO ₃ (5%), Ketjen Black (8wt%), Teflon (7wt%) to an areal density of 2.5mg/ The positive electrode sheet of cm ² is combined with a solid electrolyte containing an interface functional layer and a metal lithium sheet to assemble a button battery, wherein the interface functional layer is located between the positive electrode sheet and the solid electrolyte.

Comparative Example 4

Comparative example 4 proposes a lithium ion battery, and its preparation method includes the following steps:

Coated with LiNi _0.8 Co _0.15 Al _0.05 O ₂ (80wt%), Li _0.3 La _0.56 TiO ₃ (5%), Ketjen Black (8wt%), Teflon (7wt%) to an areal density of 2.5mg/ cm ² positive pole piece, Li _0.3 La _0.56 TiO ₃ oxide inorganic electrolyte, metallic lithium piece, assembled into a button battery.

Example 5

Embodiment 5 proposes a metal lithium negative electrode and a lithium ion battery containing an interface functional layer, and the preparation method includes the following steps:

1. Preparation of solid electrolytes with interfacial functional layers

(1) Mix 1,3-dioxane, lithium difluoroborate oxalate (LiDFOB), EC/DMC (volume ratio 1:1) uniformly in a mass ratio of 61:18:21 and place in a beaker , stirring at 600rpm for 8h to form a homogeneous solution.

(2) After the stirring is completed, the homogeneous solution is uniformly coated on the surface of Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ (LAGP) by spraying, so that the homogeneous solution fully covers and infiltrates the Li _1.5 Al _0.5 Ge _1.5 ( PO ₄ ) ₃ (LAGP).

(3) 12 minutes after pretreatment, heating and curing, the curing temperature is 45°C, to obtain a solid electrolyte containing a Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ (LAGP) interface functional layer, wherein the thickness of the interface functional layer is 900 nm .

2. Preparation of lithium-ion batteries

A positive electrode with an areal density of 4 mg/cm ² was coated with lithium manganate (LiMnO ₂ ) (83 wt %), LAGP solid electrolyte (5 wt %), Ketjen black (6 wt %), and polyvinylidene fluoride (6 wt %). sheet, with pretreated Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ interfacial functional layer of solid electrolyte and metal lithium ribbon, using the existing lamination process to make a soft-pack solid-state lithium ion battery, wherein Li _1.5 Al _0.5 The Ge _1.5 (PO ₄ ) ₃ interfacial functional layer is located between the solid electrolyte and the metallic lithium ribbon.

Comparative Example 5

Comparative example 5 proposes a lithium ion battery, and its preparation method includes the following steps:

A positive electrode with an areal density of 4 mg/cm ² was coated with lithium manganate (LiMnO ₂ ) (83 wt %), LAGP solid electrolyte (5 wt %), Ketjen black (6 wt %), and polyvinylidene fluoride (6 wt %). sheet, with traditional Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ solid-state electrolyte and metal lithium ribbon, and using the existing lamination process to make a soft-pack solid-state lithium ion battery, wherein Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ The interfacial functional layer is located between the solid electrolyte and the metallic lithium ribbon.

Example 6

Embodiment 6 proposes a solid electrolyte and a lithium ion battery containing an interface functional layer, and the preparation method includes the following steps:

1. Preparation of solid electrolytes with functional layers on both sides

(1) The ratio of 1,3-dioxane, LiPF ₆ /LiTFSI (mass ratio 2:1), EC/DEC/DME (volume ratio 1:1:1) by mass ratio is 51:18:31 After mixing evenly, it was placed in a beaker and stirred at a speed of 500 rpm for 15 h to form a homogeneous solution.

(2) Immerse the Li _6.4 La ₃ Zr _1.4 Ta _0.6 O ₁₂ solid electrolyte sheet in the above homogeneous solution to ensure that the homogeneous solution fully covers and soaks the Li _6.4 La ₃ Zr _1.4 Ta _0.6 O ₁₂ solid electrolyte sheet.

(3) After 19 min of pretreatment, the Li _6.4 La ₃ Zr _1.4 Ta _0.6 O ₁₂ solid electrolyte sheet was taken out from the homogeneous solution and cured at 50°C to obtain a solid electrolyte with an interface functional layer on both sides. The thickness of the layer is 1 in .

2. Preparation of lithium-ion batteries

Coated with LiNi _0.6 Co _0.6 Mn _0.2 O ₂ (72wt%), Li _6.4 La ₃ Zr _1.4 Ta _0.6 O ₁₂ solid electrolyte (11wt%), Super-P (9wt%), PVDF-HFP (8wt%) to form areal density It is a 3mg/cm ² positive pole piece, with Li _6.4 La ₃ Zr _1.4 Ta _0.6 O ₁₂ solid electrolyte containing functional layers on both sides, and a metal lithium negative electrode, and a button lithium ion battery is made by using the existing technology.

Example 7

Embodiment 7 proposes a solid electrolyte and a lithium ion battery, the preparation method of which includes the following steps:

1. Preparation of solid electrolytes with functional layers on both sides

(1) 1,3-dioxane, LiPF ₆ /LiTFSI (mass ratio 2:1), EC/DEC/DME (volume ratio 1:1:1) in a mass ratio of 91:5:4 After mixing evenly, it was placed in a beaker and stirred at a speed of 500 rpm for 15 h to form a homogeneous solution.

(3) The Li _6.4 La ₃ Zr _1.4 Ta _0.6 O ₁₂ solid electrolyte sheet was taken out from the homogeneous solution for 19 minutes of pretreatment, and cured at 50°C to obtain a solid electrolyte with an interface functional layer on both sides, wherein each interface functional layer The thickness is 600nm.

2. Preparation of lithium-ion batteries

Example 8

Embodiment 8 proposes a metal lithium negative electrode and a lithium ion battery containing an interface functional layer, and the preparation method includes the following steps:

1. Preparation of metallic lithium anode with interfacial functional layer

(1) Mix 1,4-dioxane, LiPF ₆ /LiFSI (mass ratio 1:1), DME, and nano-silica according to the mass ratio of 81:28:50:3 and place them in a beaker , uniformly stirred at 1000 rpm for 1 h to form a homogeneous solution.

(2) Immerse the lithium ribbon containing the Cu current collector in the homogeneous solution after the stirring is completed, so that the homogeneous solution fully covers the immersed lithium ribbon.

(3) 6 minutes after the pretreatment, the lithium ribbon is taken out from the homogeneous solution and cured at room temperature to obtain a metal lithium negative electrode containing an interface functional layer, wherein the thickness of the interface functional layer is 500 nm.

2. Preparation of lithium-ion batteries

Coated with lithium nickelate (Li ₂ NiO ₂ ) (80wt%), polyester polymer electrolyte (12wt%), conductive carbon black (3wt%), graphene (2wt%), polyvinylidene fluoride (3wt%) A positive electrode sheet with an areal density of 15 mg/cm ² is laminated with a polymer electrolyte and a treated Cu current collector lithium tape containing a functional layer in sequence, and a soft-packed lithium ion battery is made by using the existing winding process.

The lithium metal negative electrode containing the interface functional layer of Example 8 was assembled into a lithium symmetric battery, and a cycle test was carried out on it, and the results are shown in Figure 6 .

Comparative Example 6

Comparative Example 6 proposes a lithium metal negative electrode and a lithium ion battery. The difference between Comparative Example 6 and Example 8 is only that in Comparative Example 6, 1,4-dioxane, LiPF ₆ /LiFSI (mass ratio 1:1) ), DME, and nano-silica in a mass ratio of 45:4:6:13, and other preparation methods and parameters are the same.

Comparative Example 7

Comparative Example 7 proposes a lithium metal negative electrode and a lithium ion battery. The difference between Comparative Example 7 and Example 8 is only that in Comparative Example 7, 1,4-dioxane, LiPF ₆ /LiFSI (mass ratio 1:1) ), DME, and nano-silica in a mass ratio of 30:5:20:13, and other preparation methods and parameters are the same.

Comparative Example 8

Comparative Example 8 proposes a lithium metal negative electrode and a lithium ion battery. The difference between Comparative Example 8 and Example 8 is only that in Comparative Example 8, 1,4-dioxane, LiPF ₆ /LiFSI (mass ratio 1:1) ), DME, and nano-silica in a mass ratio of 20:10:8:8, and other preparation methods and parameters are the same.

The AC impedance, cycle life, Coulomb efficiency and battery short-circuit rate of the lithium-ion batteries of Examples 1-8 and Comparative Examples 1-8 of the present application at room temperature were tested respectively. The results are shown in Table 1.

Table 1

As shown in Table 1, it can be seen from the comparison of the examples and the comparative examples that the lithium ion battery of the present application has a lower interface impedance by providing an interface functional layer between the positive electrode and/or the negative electrode and the solid electrolyte, and has a higher The cycle efficiency and cycle stability of the battery are almost zero at the same time.

As shown in FIG. 5 , compared with Comparative Example 5, the AC impedance at room temperature is smaller in Example 5, indicating that the interface performance is excellent and the overall performance is excellent.

As shown in Figure 6, the lithium symmetric battery of Example 8 showed good stability in the voltage platform within 200 cycles, and no short circuit occurred. It shows that the interface stability between the negative electrode piece and the electrolyte prepared in Example 8 of the present application is good, and the growth of lithium dendrites can be well inhibited.

To sum up, the interface functional layer of the present application can improve the grain boundary resistance and electrode interface performance by adjusting the composition and ratio of raw materials, suppress the uneven deposition of lithium ions at the interface voids, reduce the interface impedance, and improve the interface stability at the same time . The lithium ion battery prepared by using the above-mentioned interface functional layer suppresses the uneven deposition of lithium ions at the interface voids, reduces the interface impedance, and improves the interface stability at the same time. The lithium-ion battery of the present application has higher cycle efficiency and cycle stability, while the battery short-circuit rate is almost zero.

The above summary of the description summarizes the features of several embodiments that may enable those of ordinary skill in the art to better understand various aspects of the application. One of ordinary skill in the art can readily use this application as a basis for designing or modifying other compositions for carrying out the same purposes and/or achieving the same advantages as the embodiments disclosed herein. Those with ordinary knowledge in the technical field can also understand that these equivalent examples do not deviate from the spirit and scope of the application, and they can make various changes, substitutions and modifications to the application without departing from the spirit of the application. with category. Although the methods disclosed herein have been described with reference to specific operations performed in a specific order, it should be understood that these operations may be combined, subdivided, or reordered to form equivalent methods without departing from the teachings of the present application. Accordingly, unless specifically indicated herein, the order and grouping of operations are not limitations of the present application.

The embodiments of the present application have been described above. However, the present application is not limited to the above-mentioned embodiment. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included within the protection scope of this application.

Claims

An interface functional layer, wherein the interface functional layer comprises a cyclic ether compound, a lithium salt, an auxiliary agent and a ceramic powder in a mass ratio of 50-90:5-30:5-40:0-5.
The interface functional layer according to claim 1, wherein the thickness of the interface functional layer is 10 nm-10 μm.
The interface functional layer according to claim 2, wherein the thickness of the interface functional layer is 400nm-800nm.
The interface functional layer according to any one of claims 1-3, wherein the particle size of the ceramic powder is 1-900 nm.
The interface functional layer according to claim 4, wherein the particle size of the ceramic powder is 500-600 nm.
The interface functional layer according to any one of claims 1-5, wherein the cyclic ether compound is selected from 1,3-dioxane and/or 1,4-dioxane; and/or,

The lithium salt is selected from lithium perchlorate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium bis-oxalate borate, lithium oxalate difluoroborate, lithium bis-difluorosulfonimide, lithium bis-trifluoromethanesulfonate Lithium imide, lithium trifluoromethanesulfonate, bismalonate boric acid, lithium oxalate borate malonate, lithium hexafluoroantimonate, lithium difluorophosphate, 4,5-dicyano-2-trifluoromethane One or more combinations of lithium imidazolium, LiN(SO 2 CF 3 ) 2 , LiN(SO 2 C 2 F 5 ) 2 , LiC(SO 2 CF 3 ) 3 and LiN(SO 2 F) 2 ; and /or,

The auxiliary agent is selected from one or more combinations of ethylene glycol dimethyl ether, dipropylene glycol dimethyl ether carbon, ethylene acid, propylene carbonate, dimethyl carbonate and diethyl carbonate; and/or,

The ceramic powder is selected from one or several combinations of nano-hexagonal boron nitride, nano-alumina and nano-silicon dioxide.
The preparation method of the interface functional layer according to any one of claims 1-6, wherein, comprising the steps of:

After the cyclic ether compound, lithium salt, auxiliary agent and ceramic powder are mixed uniformly, they are attached to the positive electrode, the negative electrode and/or the solid electrolyte and cured to obtain an interface functional layer.
The method for preparing an interface functional layer according to claim 7, wherein the negative electrode is selected from at least one of a metal lithium negative electrode or a lithium alloy negative electrode, and the metal lithium is selected from molten metal lithium, lithium powder and lithium ribbon One of the lithium alloys includes Li-In alloys, Li-Al alloys, Li-Sn alloys, Li-Mg alloys and Li-Ge alloys.
The method for preparing an interface functional layer according to claim 7 or 8, wherein the mixing is performed under stirring conditions, and the stirring speed is 200-1000 rpm/min.
The preparation method of the interface functional layer according to claim 9, wherein the stirring time is 1-24h.
The method for preparing an interface functional layer according to any one of claims 7-10, wherein the method of attachment is selected from one or more combinations of blade coating, spray coating, casting and soaking.
The preparation method of the interface functional layer according to any one of claims 7-11, wherein the temperature of the curing treatment is 25-60°C.
A lithium ion battery is prepared by winding or stacking a positive electrode, a solid electrolyte, and a negative electrode, wherein the negative electrode and/or the positive electrode and the solid electrolyte are also provided with any one of claims 1-6. Interface function layer.